'Could it be that the bluestones were already an existing stone circle that were uprooted and moved to Stonehenge?'
The bluestones have been moved around at Stonehenge haven't they? and they were also chipped about on site. But I don't know whether they were cut when they first arrived, or later on when they were moved again. Because would make a difference ? - if they were valued as a stone circle elsewhere, would you want to tidy them up when they got to Wiltshire? maybe you wouldnt or maybe you would.
Also if the stones were thought of as healing at the time, I would have been selling those chips not letting them lie around - wouldn't they contain some of the healing benefit?
But presumably they'd have this healing reputation when they were first brought over.. if we're saying that's the reason behind them being lugged all the way from Pembrokeshire.